Nucleosomal stability and dynamics vary significantly when viewed by internal versus terminal labels
Nucleosomal stability and dynamics vary significantly when viewed by internal versus terminal labels
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DOI：
10.1021/bi8000775
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发表时间：
2008-09-09
期刊：
影响因子：
2.9
通讯作者：
Lohr, D.
中科院分区：
文献类型：
--
作者：
Kelbauskas, Laimonas;Sun, Jenny;Lohr, D.
核小体是调节因子活性的主要障碍，因此也是真核生物基因组过程运作的主要障碍。一种建议的克服体内核小体阻遏的机制是因子介导的从核小体去除H2 A/H2 B。使用内部标记的FRET荧光团的核小体，我们以前观察到显着的，DNA序列依赖性的变化，在稳定性和动力学的条件下（亚纳摩尔浓度），据报道，产生H2 A/H2 B从核小体释放。在这里，使用含有监测末端区域的FRET标记的5S和MMTV-B核小体重复相同的分析方法。结果表明，核小体内的稳定性和动力学变化显着;末端标记的结构报告显着降低的稳定性和增强的DNA动力学相比，内部标记的结构。这些数据也强烈支持先前的建议（1）亚纳摩尔浓度导致H2 A/H2 B从核小体（包括5S）释放，以及（2）5S和两种启动子衍生的核小体（MMTV-B，GAL 10）内部区域的稳定性不同。序列依赖性核小体稳定性/动力学差异可能会产生内在的变化，在体内组蛋白相关的DNA的可及性。这种内在变异还可以提供一种机制，通过影响大染色质区域的过程对特定核小体产生增强的作用，从而促进关键调控序列上核小体改变的局部靶向。结果清楚地表明了研究生理相关核小体的重要性。
Nucleosomes are a major impediment to regulatory factor activities and therefore to the operation of genomic processes in eukaryotes. One suggested mechanism for overcoming in vivo nucleosomal repression is factor-mediated removal of H2A/H2B from nucleosomes. Using nucleosomes labeled internally with FRET fluorophores, we previously observed significant, DNA sequence-dependent variation in stability and dynamics under conditions (subnanomolar concentrations) reported to produce H2A/H2B release from nucleosomes. Here, the same analytical approaches are repeated using 5S and MMTV-B nucleosomes containing FRET labels that monitor the terminal regions. The results show that stability and dynamics vary significantly within the nucleosome; terminally labeled constructs report significantly reduced stability and enhanced DNA dynamics compared to internally labeled constructs. The data also strongly Support previous suggestions (1) that subnanomolar concentrations cause H2A/H2B release from nucleosomes, including the 5S, and (2) that stabilities in the internal regions of 5S and two promoter-derived nucleosomes (MMTV-B, GAL10) differ. Sequence-dependent nucleosome stability/dynamics differences could produce inherent variations in the accessibility of histone-associated DNA in vivo. Such intrinsic variation could also provide a mechanism for producing enhanced effects on specific nucleosomes by processes affecting large chromatin regions, thus facilitating the localized targeting of alterations to nucleosomes on crucial regulatory sequences. The results demonstrate clearly the importance Of Studying physiologically relevant nucleosomes.